Method and apparatus for transmitting pictures



Feb. 3, 1931. T. w. CASE 1,790,898

METHOD AND APPARATUS FOR TRANSMITTING PICTURES Filed Aug. 25, 1925' I5Sheets-Sheet l 72 flmplifler IOCycZe Genera-or fludwn oscillaiz'ny sasiem 7 I ,5

5' Hm I JEL 5 I zvrs/vroR TTOR E YS Feb. 3, 1931. 'r. w. CASE 1,790,898

METHOD AND APPARATUS FOR TRANSMITTING PICTURES Filed Aug. 25, 1925 5Sheets-Sheet 2 I 0 Eye 1e Generafor iilllhLlE} fludion osczllaizngSysiem I VE/VTOR J60 M Feb. 3, 1931. T. w. CASE 1,790,898

METHOD AND APPARATUS FOR TRANSMITTING PICTURES Filed Aug. 25, 1925 5Sheets- Sheet s & 5i Fa flmplifz'er IX/ 55 ii-"20 30 Cy cZe Generazon afludion oscillaizng sys zem 1- z z/ve gwozzu J7 dR/VEVS Patented I Feb.3, 1931 UNITED STATES PATENT OFFICE THEODORE WILLARD CASE, OF AUBURN,NEW YORK, ASSIGNOR TO CASE RESEARCH LABORATORY INCORPORATED, OF AUBURN,NEW YORK, A CORPORATION OF NEW 7 YORK Application filed August 25, 1925.Serial No. 52,381.

This invention relates to a method and apparatus for transmittingpictures, motion pictures, or direct vision over either radio or wire.

The main object of the invention is the production of a method andapparatus by means of which pictures, motion-pictures or direct visioncan be transmitted in an efficient and satisfactory manner by eitherradio or wire.

Other objects and advantages relate to the details of the method andapparatus, all as will more fully appear from the following descriptiontaken in connection with the accompanying drawings, in which Figures 1,2 and 3 are diagrammatic illustrations of embodiments of this invention.

The transmitting apparatus of Figure 1 includes a bulb -1 of glass orsimilar material, preferably having a substantially fiat end 2. The bulb1 encloses a filament 3 adapted to be heated in any suitable manner. asby a source of potential 4 and the filament is connected in circuit witha metal cylinder 5 located within the bulb 1 and adjacent the filament,but as here shown, separated from it by a disk 6 having a relativelysmall opening aligned with the apex of the filament and with the conduitthrough the cylinder 5, such circuit including a source of potential.

Within the bulb 1 and above the cylinder 5 are two plates 7 parallel toeach other so that electrons emitted by the filament and passing thruthe cylinder 5will also pass 4 between the plates 7. Above the plates 7there is placed another pair of plates 8 parallel to each other anddisposed at substantially right angles to the plates 7 and so positionedthat the stream of electrons emitted by the filament and passing throughthe cylinder 5 and between plates -7 will also pass between the plates8. y

As shown, one plate of each pair is electrically connected to thecylinder 5. The end 2 of the bulb or bottle 1 has a coating 9 in theform of a semi-transparent or opaque layer of some conductingphoto-electric material, such as potassium or any material which emitselectrons under the influence of light. A substantial vacuum ismaintained within the bulb 1 altho it should be understood that thevacuum may not be the highest obtainable as a small quantity of gas ispreferred to prevent the electron stream emitted by the filament fromspreading, and to keep it as a small pointer This transmitting apparatusis primarily based on the effect of photo-electric 'emission upon .astream or quanta of electrons, preferably thermo-electrons, and makesuse of a stream or pointer of such thermo-electrons emitted from aheated filament. The stream of electrons is pro- METHOD AND APPARATUSFOR TRANSMITTING PICTURES W fi duced by the filament cathode 3, whichmay be oxide-coated and is heatedas described. After leaving thefilament the electrons may pass through the small aperture of the metalshield 6 which concentrates them into a thin stream so that they maypass through the tubular anode 5.

The movement of the pointer is controlled by electric fields applied tothe plates 7 and 8. An electric field applied to the plates 7 willdeflect the electron pointer in one direction and an electric fieldapplied to the plates 8 will deflect the electron pointer in anotherdirection, and as here illustrated, these two deflecting directions areat right angles to each other. The result is that at any instant therecording point forming the end of the stream of electrons occupies aposition on the photo-electric layer 9 which both in direction anddistance from its normal position at the center is theresult of thedeflecting forces due to the differences of potential acting at thatinstant on the two pairs of plates. i

In addition to its deflection by an electric field, the electron streamcan be deflected by a magnetic field by using outside of the tube eithera permanent magnet or pair of coils in which the current is flowing.

The picture which is to be transmitted is focused upon the layer 9 ofphoto-electric material, and if the layer 9 is semi transparcut, thepicture or image may be focused right through the coatin (lens 10illustrated for that purpose). n case the layer 9 is thick enough to beopaque, the picture to be transmitted is focused upon the potassium orcoating 9 on the side facing the electron stream,-lens 11 illustratedbeing for that pur ose.

iththe picture focused through or upon the photo-electric coating 9, thefirst essential thing is to cover the entire picture with the electronstream in approximately 1/l0th of a second, or reater i. e. a speedproductive of direct vision. This may be accomplished by impressingelectro-statlc variations from an alternating current on both the pairsof plates 7 and'8. The cycle of' one current need not, be greater thanapproximately 8 to cycles. For illustrative purposes, I will describethe operation in connection with an alternating current of 10 cyclesimpressed on the plates 8.

The result 'f this impressed current on the lates 8 is that the electronointer will go back and forth over the en 2 of the bulb and over thepicture ten times per second, but only in a single line. Assuming apicture 6" x 6", and the condition that it is desirable to break-up thepicture into 100 different lines to the. inch, that would mean thatthere would have to be 600 lines across the picture.

If the first electro-static field which is applied to the plate 8 causesthe electron stream or pointer to traverse the picture ten tlmes persecond,- then the electron pointer crosses the picture in 1/10th of asecond. Now, in order to break this up into 600 parts, it is necessaryto divide 600 by 1/10th, or in other.

words, an alternating current of 6000 cycles per second must be appliedto plate 7 Thls alternating current of the required number x of cyclesmay be produced in any suit-able and well known manner, as for instance,by an audion oscillating system, whereas the alternating current appliedto the plates 8 altho producible in various known ways, may

be-produced by an ordinary 10 cycle gen-' erator.- A

Under the conditions described, the entire picture focused on or throughthe coating 9 will be covered and broken u into fine lines in thenecessary time to pro uce the desired results. Q

There are several circuits which can be used in obtaining modulation inthis transmission of the picture focused on the coating 9. Perhaps thesimplest form is that connecting the photo-electric coating 9 with theheatedefilament 3 or source of the electron stream. In the firstinstance, no additional source of potential will be inserted in thiscircuit, but it may contain the primary 12 of a transformer, thesecondary of which may lead to suitable well known amplifying devices,or the coating 9 and the source of the electron stream 3 may beconnected in circuit with the filament and grid of a properly biasedaudion bulb for amplification purposes, the methods of amplification andtherequired circuits being well known.

In the circuit just described, the switch.

electric material. The units of this explorijigelectron fingeralternately arerushing towards firstan illuminated portion ofthe"photo-electric material, and next an unillu"- minated portion of thephoto-electric material, there will as a result obtain difi'erentelectrical phenomena in the completed circuit, due to'the negativeelectrons approaching different potential points on the illuminatedphoto-electric electrode 9, and minute electric currents will flow inthe complete circuit controlled by the illuminated potassium electrode.

It is at present my belief that this action is based on the law thatWhen two dlS-SlnlllflIL charges comein contact in a circuit, a minutecurrent will fiow,-contact electricity. In this manner, the picture isbroken up and translated into consecutive electron pulses which areamplified, and may then be turned back into corresponding lightfluctuations and when put back on a screen in the proper position at thereceiving .end will reproduce the picture focused on or through thephotoelectric electrode at the sending end; In

addition, these electron pulses impressed on pressed on the circuitwhich connects the fila'- ment with the cylinderandas the impulsesincrease or decrease, the intensity of the electron streamcorrespondingly increases and decreases, consequently the fluorescencein. creases and decreases in like manner, and the pattern traced invisible lines is photographically active. It is only necessary to putthese changes in intensity resulting in changes in fluorescence in theirproper position in order to re-form the picture focused on the coating 9at the sending end. This is done by making the varying intensityelectronpointer cover the fluorescent screen in the same manner and synchronizedwith the electron pointer at the sending end. This requires impressing10 cycles on one of the pairs of plates in the repair.

methods may be used that produce the movement of the electron bulb.However, other pointer in the sendin 1n synchronizing and separatefields may be used to produce the movement of the finger other than herede-' scribed.

As an alternative arrangement, there may be placed in'the receiving bulba grid large enough so that the electron pointer will always passthrough it, and then the incoming current pulses may be impressed uponthis grid to thereby control the current intensity of the electronpointer which will correspondingly control the fluorescence of thecoating corresponding to the coating 9. On the other hand, a small gridmay be placed between the filament and the cylinder to control theintensity of the electron pointer.

Altho the apparatus of Figure 1 may be utilized as above describedwithoutany extra potentiaLinthe circuit between the electrode 9 and thefilament 3, it may perhaps be i preferable to place a potential in thiscircuit making the filament 3 negative and the photoelectric electrode 9positive. This may be done by closing switch 13 and-opening switch 14.In this case the electrons as they approach an illuminated portion ormore negative sphere of influence would, as a result of the tendencynegative emission of the photo-electric material due to light, give adecreased current in this circuit and reversely an increased currentWhere the electrons impressing a direct current on the filamentphoto-electric electrode circuit to impress an oscillating carriercurrent on this circuit. This may be eflected in any suitable and wellknown manner. In this arrangement, the oscillating carrier current willbe likewise modulated as the negative electrons approach consecutive andeither more or less negative spheres of influence in the photoelectriclayer. In such case where an oscillating carrier current is used quantaof electrons will be directed to the different parts of thephotoelectric electrode 9, depending on the frequency of the pulsatingcarrier current, and

this frequency may be determined empirically for best results.

Instead of using a pulsating current, an alternating current maybeImpressed on tlns circuit. altho at present such arrangement seems lesspreferable. In case of pulsating direct current the photo-electricmaterial should be positive and the'filament negative.

There are various other combinations and circuits which may be used, butall depend on the fundamental idea of obtaining modulation of'a carriercurrent circuit depending on the charge of the sphere of influence intowhich the thermo-electron pointer is converging at any one instant oftime, which in turn depends upon the focusing of the picture on thephoto-electric electrode or coating 9. In addition, there may beamplification of the modulation so obtained and there remains onlyputting together again at the receiving end in terms of light and at theproper position to re-form the image and at a speed to produce directvision.

Obviously, a single'picture may be transmitted or a series of picturesin sufficiently rapid succession to produce direct vision. In the lattercase where a moving picture is to be transmitted it would be preferableto employ a shutter arrangement at the sending end and possibly also atthe receiving end in order to obviate any blurring. -On the other hand,a chopper carrier current might be employed instead of the shutter.

In Figure 2 there is illustrated a large grid 15 interposed between theplate electrode 16 and the filament 3 and in the path of the electronstream or pointer which is indicated in dotted lines in the figures.This grid may be formed of any suitable material. and is full of verysmall holes and is coated with a photo-electric material. The picture tobe transmitted is focused upon the photo-electric material deposited onthe grid 15 and the holes of the grid should correspond to the points ofthe picture to be transmitted. As shown. the grid 15 is disposed in aplane substantially parallel with the end of the plane 2 of the bulb.The plate electrode 16 is connected in circuit with the filament 3, andthis circuit may include the secondary of atransformer as described inconnection with Fig. 1 or the electrodes may be connected to anyamplifying means such 'as the grid filament circuit of an audion. Inaddition, the circuit connecting the plate 16 with the filament 3 neednot include any source of potential or it may include a source-of directcurrent or a source of oscillating current, or a source of alternatingcurrent. all as described in connection with the analogous cirplatefilament circuit results. In this case the electron finger may spread onemerging from the grid and make no difference so long as it is pointcontrolled at the grid on which the picture is focused. I

In addition to the connections shown in the drawings, the grid 15 mayhave an electric connection to the outside of the bulb so as to permitof biasing the grid, if desired.

The structure of Figure 3 differs from Figure 1 in the interposition ofa ring electrode 17 between the filament 3 and the photo-electriccoating or electrode 9, and as illustrated the ring 17 is connected tothe coating 9 by an electric circuit including a source of potential 18arranged in such a manner that the ring is positive and thephoto-electric coating 9 is negative, thereby producing an actualemission of electrons. The introduction ofthe exciting circuit betweenthe coating 9 and the ring electrode 17 makes the spheres of influenceof the photo-electric electrode more pronounced. This additional circuitbetween 'the ring 17 and the photo-electric electrode 9 may also beutilized in connection with the structure of Figure 2 in'that the ringmay be inserted between the grid 15 and filament 3 and may be connectedin circuit with the photo-electric coating on the grid through a sourceof potential in such ,a manner as to maintain the rin positive and thephotoelectrode negative in the same manner as Figure 3, and for the samepurpose of effecting more pronounced results.

Any suitable and known means may be utilized in the ordinary manner forapplying an electric field of proper cycle to the plates 7 and 8, forinstance, as described, a generator or an audion oscillating system.Altho I have shown and described in a diagrammatic manner specificstructures and arrangement of apparatus and the parts thereof, asinstancing embodiments of this invention, I do not desire to restrictmyself to the details of the structure or the specific method ofoperation described, as various changes may be made within the scope ofthe appended ,claims.

Picture as used in the claims hereof -is deemed to include any picture,direct vision, object or image that canbe produced or be focused on thephoto-electric layer, and focusing is deemed to include any suitablemeans of producing such picture on such coating.

1 claim 1. The method of transmitting pictures, motion-pictures ordirect vision comprising causing an electron stream to traverse thepicture when the latter is focused upon a photo-electric material havinga negative po tential maintained thereon.

2. An apparatus for transmitting pictures, motion-pictures or directvision, comprising a filamentary cathode, an anode of tubular form, acircuit connecting the cathode and the anode, and including a source ofpotential,

means for deflecting the stream of electrons emitted by the cathode,a'photo-electric layer over which said electron stream as deflected isadapted to pass and upon which the picture is adapted to be focused, anda circuit connecting the photo-electric layer and the cathode.

3. An apparatus for transmitting pictures, motion-pictures or directvision, comprising a filamentary cathode, an anode of tubular form, acircuit connecting the cathode and the anode, and including asource ofpotential, means for deflecting the stream of electrons emitted by thecathode, a photo-electric layer over which said electron stream asdeflected isadapted to pass and upon which the picture is adapted to befocused,a circuit connecting the photo-electric layer and the cathode,and means for maintaining the photo-electric layer negative.

4. An apparatus of the class described comprising an elongated bulbhaving a substantially flat end, a coating of photo-electric material onthe interior of theflat end of said bulb, a cathode within the bulb, atubular anode within the bulb arranged to direct the stream of electronsemitted by the cathode toward the said photo-electric coating, means fordeflecting said stream of electrons in'different directions andmeans forfocusing a picture upon said photo-electric coating, and a circuitconnecting'the photo-electric coating and the cathode.

5. An apparatus of the class described comprising an elongated bulbhaving a substantially flat end, a coating of photo-electric material onthe interior of the flat end of said bulb, a cathode within the bulb,atubular anode within the bulb arranged to direct the stream ofelectrons emitted by the cathode toward the said photo-electric coating,means for deflecting said stream of electrons in different directions,and means for focusing a picture upon said photo-electric coating, acircuit connecting the photo-electric coating and the cathode, and meansfor impressing an electric current'on said circuit.

6. An apparatus of the class described, comprising an elongated bulbhaving a sub stantially flat end, a coating of photo-electric materialon the interior of the flat end of said bulb, a cathode within the bulb,a tubular anode within the bulb arranged to direct the stream ofelectrons emitted by the cathode toward the said photo-electric coating,an opaque disc having a small opening positioned between said anode andcathode, said opening being in line with the opening of the anode andthe apex of the cathode, a pair of spaced parallel plates positionedbetween said anode and said photo-electric coating, a second pair ofspaced parallel plates having their plane surfaces at right angles tothe plane surfaces of the first-named plates and positioned adjacent thesame on the side of the photo-electric coating means for deflectin saidelectron stream l y energizing said pairs of plates with a high and lowfrequency alternating current respectively means for focusing a pictureupon said photo-electric coating, :1 clrcuit connecting thephoto-electric coating and the cathode and means for impressing anelectric current on said circuit.

In witness whereof I have hereunto set my 10 hand this 17th day of Aust, 1925.

THEODORE ARD CASE.

DISCLAIM ER 1,790,898.I7re0d0re Willard Case, Auburn N. Y. METHOD ANDAPPARATUS FOR Tmsm'rrmo Prc'nmns. Patent dated February 3, 1931.Disclaimer filed August 22, 1939, by the inventor; the co, (JaseResearch Laboratory, I consenting. Herelg enters a disclaimer to claim 2of said Letters Patent.

[ final Gazette September 1.9, 1939.]

